1 / 20

Yan Lu for STAR collaboration Department of Modern Physics

System Size Dependence of Strange Hadron Elliptic Flow from 200 GeV Au + Au and Cu + Cu collisions. Yan Lu for STAR collaboration Department of Modern Physics University of Science and Technology of China. Quark Matter 2008 The 20 th International Conference on

sahara
Télécharger la présentation

Yan Lu for STAR collaboration Department of Modern Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. System Size Dependence of Strange Hadron Elliptic Flow from 200 GeV Au + Au and Cu + Cu collisions Yan Lu for STAR collaboration Department of Modern Physics University of Science and Technology of China Quark Matter 2008 The 20th International Conference on Ultra-relativistic Nucleus-Nucleus Collisions February 4–10, Jaipur, India

  2. Outline • Motivation • Data analysis • Results and Discussion • Summary and Outlook Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  3. Low density limit: 1 dN  e v 2 S dy In case of thermalization:  e v2 2 part is for the participant zone. Thermalization? ‘We argue that the centrality dependence of elliptic flow should be a good indicator of the degree of equilibration reached in the action. ’ S. Voloshin, A. Poskanzer, PLB 474, 27, 2000. Data: S. Voloshin, nucl-ex/ 0701038 Hydro: Kolb, Sollfrank, Heinz, PRC 62 (2000) 054909 • Possible thermalization only for the most central collisions. Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  4. Partonic Collectivity at RHIC minimum bias ‘They are made via coalescence of seemingly thermalized quarks in central Au+Au collisions, the observations imply hot and dense matter with partonic collectivity has been formed at RHIC’ STAR: Phys. Rev. Lett., 99, 112301(07), nucl-ex/0703033 Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  5. Collectivity nq scaling Local Thermalization  Why System Size and Centrality Dependence? • versus • - Systematic study for identified hadrons will gain information on interplay of collectivity, NQ scaling and thermalization as a function of collision system size and centrality. • Determine parameters for partonic EoS. Centrality System Size Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  6. System: Au+Au collision • Energy : sNN = 200 GeV • Event sample: ~22 M events • Centrality: 0 – 80 %, 0 – 10%, 10 – 40%, 40 – 80% • System: Cu+Cu collision • Energy : sNN = 200 GeV • Event sample: ~21 M events • Centrality: 0 – 60 %, 0 – 20%, 20 – 60% Dataset and Cuts multiplicity collision centrality • Event cuts: |Vertex z| < 30cm • FTPC track cuts: 6 =< nFitHits < 12, nHitsFit/nHitsPoss > 0.52 • pT > 0.1, 2.5 < || < 4.0, Dca < 2.0 cm Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  7. PID and v2 Methods • v2 vs. minv method (background subtraction technique): - used for K0S, Λ, Ξ, , and  analysis and for Au+Au and Cu+Cu datasets • flow method - Event Plane method used for Au+Au and Cu+Cu datasets - non-flow systematic: Lee-Yang Zero method for Au+Au and Event Plane method with FTPC reaction plane for Cu+Cu Lee-Yang Zero method: R. S. Bhalerao, N. Borghini, J.-Y.Ollitrault, Nucl. Phy. A 727 (2003) 373-426 Event Plane method: A. M. Poskanzer, S. A. Voloshin, Phys. Rev. C58, 1671 (1998) Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  8. Transverse kinetic energy: mT – m = (pT)2 + m2 - m Centrality Dependence ofIdentified v2 STAR Preliminary Transverse momentum 200 GeV Au+Au • All centralities: mass ordering at low pTmT-m scaling at low mT-m. • All centralities: baryon v2 > meson v2 at intermediate pT or mT-m. Hydro: P. Huovinen, private communications, 2007 Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  9. Centrality Dependence of Number-of-Quark Scaling nq: number of quark within a hadron STAR Preliminary 200 GeV Au+Au • nq scaling is observed at all centrality bins. Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  10. (c) Eccentricity Scaling(?) 200 GeV Au+Au 200 GeV Au+Au • Not observe the part scaling claimed by PHENIX. • Divided v2 by <v2>ch instead of part, it appears that the scaling works better. • Scale by part to remove initial geometry effect. • Larger v2/part indicates stronger flow in more central collisions. STAR Preliminary PHENIX: Phys. Rev. Lett 98, 162301 (2007) Phys. Lett. B 503, 58 (2001) Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  11.   p   pT-integrated v2/part STAR Preliminary • v2/part versus Npart  data: increasing trend indicates stronger flow in more central collisions.  hydro: little sensitivity to the collision centrality as expected in equilibrium scenario. • v2/part for a given centrality  hydro: a clear hadron mass dependence.  data: not clear due to large errors. • Above Npart ~ 170, integrated v2 consistent with hydro prediction indicates local thermalization. 200 GeV Au+Au Charge particle data: STAR, Phys. Rev. C 72, 014904, 2005. Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  12. System Size Dependence STAR Preliminary PHENIX: Phys. Rev. Lett 98, 162301 (2007) See S. S. Shi’s poster • A given colliding system: clear scaling with nq. • System size dependence: - No part scaling claimed by PHENIX - v2 seems to fall at lower pT in Cu+Cu than in Au+Au Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  13. Summary • We report azimuthal anisotropy parameter v2 of strange and multi-strange hadrons from Au+Au and Cu+Cu collisions at 200 GeV. Detailed centrality dependence is presented up to pT ~ 6 GeV/c. • At low pT region, collectivity is observed at all centrality bins under study.  it follows a mT-m scaling. • Not observe the part scaling. larger v2/part indicatesstronger flow in more central collisions and larger system. • v2/part increase with Npart, reaching hydro prediction in central Au+Au collisions. indicate thermalization in central Au+Au collisions. Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  14. Future: More systematic measurements for , : partonic EoS parameters Heavy quark collectivity: early thermalization of light quarks

  15. Backup slides! Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  16. y py px x y z x Reaction plane: z-x plane Elliptic flow beam impact parameter Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  17. v2 vs minv method SIG + BG • analysis method: v2 vs. minv • motivated by Borghini et al. [nucl-th/0407041] • advantages over standard method: • only one fit per pT bin - smaller systematic uncertainties • method used for K0S, Λ, Ξ, , and  analysis • standard method and v2 vs. minv method give consistent results BG BG (SIG+BG) SIG (SIG+BG) v2TOT(minv) Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  18. TPC FTPC FTPC Systematic Errors Evaluation • Standard method (Event Plane method): - flow vector - event plane angle A. M. Poskanzer, S. A. Voloshin, Phys. Rev. C58, 1671 (1998) Sensitive to non-flow. • Lee-Yang Zero method: - measure flow using genuine correlations among all particles. - flow determined from first minimum r0 of generating function. • FTPC Reaction Plane: - Similar to Event Plane method - Correlate particles in TPC region with FTPC reaction plane. Suppress non-flow. all particles arbitrary variable Quark Matter 2008, Feb. 4 – 10, Jaipur, India R. S. Bhalerao, N. Borghini, J.-Y.Ollitrault, Nucl. Phy. A 727 (2003) 373-426

  19. Non-flow systematics • 200 GeV Au+Au 10-40%. • h± (yellow bands): decreasing trend. • PID: no clear pT and PID dependence. • v2{LYZ} < v2{EP}: ~10% effect. • 200 GeV Cu+Cu 0-60%. • v2{EP, FTPC} < v2{EP, TPC}. • larger effect at higher pT. • v2 from two methods consistent for  within large errors. Quark Matter 2008, Feb. 4 – 10, Jaipur, India

  20. System Size and Centrality Dependence PHENIX: Phys. Rev. Lett 98, 162301 (2007) STAR Preliminary • A given centrality of a colliding system: clear scaling with nq. • A given system: stronger flow in more central collisions. • Not observe the part scaling claimed by PHENIX, which is independent on colliding system . Quark Matter 2008, Feb. 4 – 10, Jaipur, India

More Related